1. Field of the Invention
The present invention relates to a speaker system having a speaker midship mount attaching structure in which a speaker unit is attached to an inner baffle board in a cabinet.
2. Description of the Prior Art
Recently, compact discs have been produced so that the performance of sources have been sharply improved. Therefore, in speaker systems for reproducing such sources, it has become necessary to improve the quality of material of diaphragms and to improve reproducing capability. To this end, a speaker system employs a speaker unit midship mount attaching structure to reduce unnecessary vibrations of a baffle board. However, a frame of a woofer additionally takes part in the unnecessary vibrations on the front of a cabinet. Except in special cases, the frame of the woofer is generally made of an aluminum alloy so that it is strong enough to hold a magnetic circuit. When a signal is applied to the speaker unit so that a driving force is applied to the diaphragm from a voice coil, the vibrations are naturally transmitted to the frame. The vibrations of the frame are also radiated into space as sound, so that an audience listens to the vibrational sound mixed with the sound transmitted from the diaphragm.
In such a system, there has been a problem with the quality of sound produced by the speaker system because of the frame vibrations. That is, the frame is ring-like on the front of the cabinet and the exposed surface area of the frame is considerably large and sometimes larger than the area of the diaphragm of a speaker, so that the vibrational sound level from the frame cannot be neglected. FIG. 3(b) shows a result of investigation of an acceleration characteristic of a woofer frame at a portion thereof on the front of the cabinet, that is, at the outermost circumferential edge surface of the woofer frame, with respect to a conventional device of the midship mount type. In this case, although a crossover frequency is 2.5 KHz, vibrations of considerably higher frequencies are radiated from the surface of the woofer. Additionally, it is believed that vibrations from a tweeter are also transmitted to the surface of the frame of the woofer.